Mobile telephony and landline telephony are currently offered as two completely separate products. Therefore, the customer also gets separate telephone numbers, which he also must use in different networks with different telephones.
In addition, different rates are offered to the customer in both networks. The result of this is that the customer, if he is, e.g., at home, he must make a decision for outgoing calls, based on these rates, of whether he wants to use the landline network or mobile telephone network.
Potential callers must be informed of two telephone numbers, while each telephone number generally has its own answering machine or voice mail. Because of this, operation and use of telecommunication services becomes complicated.
To add to this, in households with several people, with analog user connections, only a single phone number is available. In contrast, in mobile telephones there is a trend toward personalizing telephone numbers.
For transparent usage of landline network and mobile phone network, the customer today has only the rudimentary beginnings, which are mainly based on call forwarding. An example will serve as an explanation:    1. If the customer will not be available, he call forwards his mobile telephone number to a landline number. An answering machine is connected to the landline connection.    2. If the customer will not be available, he call forwards his landline number to his mobile telephone number. If he cannot be reached at the mobile telephone number, there is a call forwarding to the voice mail in the mobile telephone network.
Several serious disadvantages result from this:    1. Handling the call forwarding for the two networks has to be carried out separately.    2. The call forwarding can only be changed by using the respective terminal (landline phone for landline phone numbers and mobile phone for mobile phone numbers).